The present invention relates to overhead doors for use in buildings, especially for buildings with large openings.
Agricultural, aviation, commercial buildings and the like generally require a large opening for accommodating trucks, tractors, airplanes, large farm equipment (e.g. combines), large industrial equipment, and others, through such opening. Common types of conventional door assemblies currently used to accommodate this need include two piece center hinging cable drawn doors (bi-fold) and horizontally sliding doors that are supported by and slide on a track system. These types of conventional doors generally require a larger opening than is required to accommodate the door members, thus reducing the overall available vertical height of the building opening that can be provided for a given limited area of space or land. Furthermore, these types of doors require that the building be engineered with extra reinforcement because the load of the door is generally supported by the building itself.
The most common types of door assemblies used in buildings are the two piece center hinging cable drawn doors. Cables draw the bottom end of the door directly vertically towards the top of the door, while being guided on a track system. During the opening process, the hinged portion of the door moves in an outwardly and upwardly direction causing the bottom leaf of the door to fold underneath the top leaf. Consequently, this requires a larger building height to accommodate the desired opening. Furthermore, since the door itself is mounted to the building structure, the building bears the entire load of the door and must be reinforced accordingly. The bi-fold door also has other disadvantages because it is operated by a cable/pulley system having many moving parts, resulting in a high wear and high maintenance system. Furthermore, the bi-fold door must be locked down manually to effect a complete closure and has an inherently slow open/close cycle time, making the opening/closing process inconvenient and time consuming. Additionally, in the event of a failure of any of these mechanical components, the door may drop, thus creating a safety hazard. Moreover, the bi-fold door is drafty because it closes against the exterior of the building and the joints are exposed to the elements.
Other conventional types of door assemblies include horizontally sliding doors. These types of doors are supported by and slide on a track system. Problems also arise with these doors since the track can accumulate ice, mud and other debris that can push the door out of alignment with the track, making it difficult to operate. Once the doors are out of alignment, they are generally difficult to open and close. Moreover, horizontally sliding doors require storage space on either side of the building opening to accommodate the door leaves when the door is in the open position. The storage space required to accommodate the door leaves reduces the usable width of the building opening that can be provided for a given limited area of space or land.
Accordingly, for the foregoing reasons, there is a need for a door that pivots on a load bearing frame that is separate from the building structure such that the door does not hang on and load the building structure. There is also a need for a door that includes its own separate framework, such that loads placed on means for operating the door are transferred to the load bearing frame and not to the building structure.
There is also a need for a door that maximizes the useable space of the available opening in the building. For example, there is a need for a door that utilizes virtually no overhead or side door storage space making it possible to provide a smaller building size for a given required building opening size, or maximize an existing opening available in a building.
Furthermore, there is a need for a door member that has no moving parts such as pulleys, shafts, bearings, gear boxes, track systems or the like, thus making the door member virtually maintenance free. Also, there is a need for a door that includes means for connecting alternative power sources for operating the door in the event of an electrical power outage. There is also a need for a door that closes flush with the exterior building wall to provide a weather tight seal.